Significant changes in the range and use of primary fossil fuels throughout the world over the last years have influenced and altered the way that energy intensive industries source their requirements and operate. These industrial trends have been significantly affected by fuel economics, diversification and availability, as well as by an increasing need to improve environmental performance. Higher prices have resulted in a move away from conventional oil based fuels towards cheaper alternatives with reduced environmental impact. Although feasible primary energy alternatives to oil exist for land-based industries, the shipping market remains predominantly dependent on oil-based products, particularly heavy fuel oil-based products, and is likely to do so for the foreseeable future.
Heavy fuel oils are normally produced by blending viscous refinery residues with higher value distillate fuels to provide the lower viscosity characteristics required for acceptable fuel handling and combustion performance. Direct use of high viscosity refinery residues requires high-temperature storage and handling that limits and complicates their potential use, and consequently lowers their value. As an alternative to blending refinery residues for fuel oil production, further processing (e.g. coking, hydrocracking, etc.) of the residue can be applied at the refinery to yield additional distillate fuels. However this strategy requires large capital investments to be made by the oil refinery, produces some lower value products, generates difficult to market by-products, results in an increase of emissions (including greenhouse and acid gases), all of which can serve to limit the economic advantage of this approach.
Preparation of emulsion fuels has been previously described, for example in Logaraj et al; “Emulsification—A solution to Asphaltene Handling Problems”, presented at the ISSA/AEMA 2nd Joint Conference, Mar. 12-13, 2000, Amelia Island, Florida, GB 2 475 090, U.S. Pat. Nos. 4,776,977, 5,419,852, 5,603,864, 6,530,965 B2, US 2010/0043277 A, U.S. Pat. Nos. 5,411,558, 5,360,458, 5,437,693, 5,976,200 and 6,113,659. Droplet size distribution characteristics of an emulsion fuel and the resulting combustion performance has been previously described in WO 2008/074138, EP 1 935 969 and U.S. Pat. No. 5,603,864. WO 2014/082981 describes Bitumen emulsions, and U.S. Pat. No. 6,194,472 describes colloidal dispersions of hydrocarbons in water, in which softening point of the hydrocarbons in the dispersion exceeds about 95° C.
There remains a need for an oil-in-water emulsion, particularly an oil-in-water emulsion fuel, and more particularly a marine fuel, that has improved stability during storage and handling.